污染场地环境水文地质勘察的技术要求及应用探讨

随着城市化的进程加快,大量工业企业地块用地性质发生变更,对于此类污染地块需要依次开展土壤污染状况调查、风险评估、风险管控或修复治理、效果评估等工作,而环境水文地质勘察工作贯穿了整个环境管理环节,是土壤污染调查评估、修复治理的重要内容。本文旨在对水文地质勘察工作的技术要求及其应用进行论述,促进环境领域水文地质勘察技术的发展。     

Molecular Dissection of Escherichia coli CpdB: Roles of the N Domain in Catalysis and Phosphate Inhibition,and of the C Domain in Substrate Specificity and Adenosine Inhibition

CpdB is a 3′-nucleotidase/2′3′-cyclic nucleotide phosphodiesterase, active also with reasonable efficiency on cyclic dinucleotides like c-di-AMP (3′,5′-cyclic diadenosine monophosphate) and c-di-GMP (3′,5′-cyclic diadenosine monophosphate). These are regulators of bacterial physiology, but are also pathogen-associated molecular patterns recognized by STING to induce IFN-β response in infected hosts. The cpdB gene of Gram-negative and its homologs of gram-positive bacteria are virulence factors. Their protein products are extracytoplasmic enzymes (either periplasmic or cell–wall anchored) and can hydrolyze extracellular cyclic dinucleotides, thus reducing the innate immune responses of infected hosts. This makes CpdB(-like) enzymes potential targets for novel therapeutic strategies in infectious diseases, bringing about the necessity to gain insight into the molecular bases of their catalytic behavior. We have dissected the two-domain structure of Escherichia coli CpdB to study the role of its N-terminal and C-terminal domains (CpdB_Ndom and CpdB_Cdom). The specificity, kinetics and inhibitor sensitivity of point mutants of CpdB, and truncated proteins CpdB_Ndom and CpdB_Cdom were investigated. CpdB_Ndom contains the catalytic site, is inhibited by phosphate but not by adenosine, while CpdB_Cdom is inactive but contains a substrate-binding site that determines substrate specificity and adenosine inhibition of CpdB. Among CpdB substrates, 3′-AMP, cyclic dinucleotides and linear dinucleotides are strongly dependent on the CpdB_Cdom binding site for activity, as the isolated CpdB_Ndom showed much-diminished activity on them. In contrast, 2′,3′-cyclic mononucleotides and bis-4-nitrophenylphosphate were actively hydrolyzed by CpdB_Ndom, indicating that they are rather independent of the CpdB_Cdom binding site.     

Fe?N?C Electrocatalysts with Densely Accessible Fe?N4 Sites for Efficient Oxygen Reduction Reaction

The development of iron and nitrogen co-doped carbon (Fe N C) electrocatalysts for the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs) is a grand challenge due to the low density of accessible Fe N₄ sites. Here, an in situ trapping strategy using nitrogen-rich molecules (e.g., melamine, MA) is demonstrated to enhance the amount of accessible Fe N₄ sites in Fe N C electrocatalysts. The melamine molecules can participate in the coordination of Fe ions in zeolitic imidazolate frameworks to form Fe N₆ sites within precursors. These Fe N₆ sites are then converted into atomically dispersed Fe N₄ sites during a pyrolytic process. Remarkably, the Fe N C/MA exhibits a high single-atom Fe content (3.5 wt.%), a large surface area (1160 m² g⁻¹), and a high density of accessible FeN₄ sites (45.7 × 10¹⁹ sites g⁻¹). As a result, Fe N C/MA shows a much enhanced ORR activity with a half-wave potential of 0.83 V (vs the reversible hydrogen electrode) in a 0.5 m H₂SO₄ electrolyte solution and a good performance in a PEMFC system with an activity of 80 mA cm⁻² at 0.8 V under 1.0 bar H₂/air. This work offers a promising approach toward high-performance carbon-based ORR electrocatalysts.     

Biomolecular Simulations with the Three-Dimensional Reference Interaction Site Model with the Kovalenko-Hirata Closure Molecular Solvation Theory

The statistical mechanics-based 3-dimensional reference interaction site model with the Kovalenko-Hirata closure (3D-RISM-KH) molecular solvation theory has proven to be an essential part of a multiscale modeling framework, covering a vast region of molecular simulation techniques. The successful application ranges from the small molecule solvation energy to the bulk phase behavior of polymers, macromolecules, etc. The 3D-RISM-KH successfully predicts and explains the molecular mechanisms of self-assembly and aggregation of proteins and peptides related to neurodegeneration, protein-ligand binding, and structure-function related solvation properties. Upon coupling the 3D-RISM-KH theory with a novel multiple time-step molecular dynamic (MD) of the solute biomolecule stabilized by the optimized isokinetic Nosé–Hoover chain thermostat driven by effective solvation forces obtained from 3D-RISM-KH and extrapolated forward by generalized solvation force extrapolation (GSFE), gigantic outer time-steps up to picoseconds to accurately calculate equilibrium properties were obtained in this new quasidynamics protocol. The multiscale OIN/GSFE/3D-RISM-KH algorithm was implemented in the Amber package and well documented for fully flexible model of alanine dipeptide, miniprotein 1L2Y, and protein G in aqueous solution, with a solvent sampling rate ~150 times faster than a standard MD simulation in explicit water. Further acceleration in computation can be achieved by modifying the extent of solvation layers considered in the calculation, as well as by modifying existing closure relations. This enhanced simulation technique has proven applications in protein-ligand binding energy calculations, ligand/solvent binding site prediction, molecular solvation energy calculations, etc. Applications of the RISM-KH theory in molecular simulation are discussed in this work.     

Multiple Recombination Events and Strong Purifying Selection at the Origin of SARS-CoV-2 Spike Glycoprotein Increased Correlated Dynamic Movements

Our evolutionary and structural analyses revealed that the severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) spike gene is a complex mosaic resulting from several recombination events. Additionally, the fixation of variants has mainly been driven by purifying selection, suggesting the presence of conserved structural features. Our dynamic simulations identified two main long-range covariant dynamic movements of the novel glycoprotein, and showed that, as a result of the evolutionary duality, they are preserved. The first movement involves the receptor binding domain with the N-terminal domain and the C-terminal domain 2 and is maintained across human, bat and pangolin coronaviruses. The second is a complex network of long-range dynamics specific to SARS-CoV-2 involving the novel PRRA and the conserved KR*SF cleavage sites, as well as conserved segments in C-terminal domain 3. These movements, essential for host cell binding, are maintained by hinges conserved across human, bat, and pangolin coronaviruses glycoproteins. The hinges, located around Threonine 333 and Proline 527 within the N-terminal domain and C-terminal domain 2, represent candidate targets for the future development of novel pan-coronavirus inhibitors. In summary, we show that while recombination created a new configuration that increased the covariant dynamic movements of the SARS-CoV-2 glycoprotein, negative selection preserved its inter-domain structure throughout evolution in different hosts and inter-species transmissions.     

防砂埋套管水力喷射泵研制

水力喷射泵具有独特的井液举升特点,适用于斜井、高温、稠油、出砂、结蜡和腐蚀等复杂情况的油井[1]。但用于携排砂生产,易发生埋封隔器造成油井大修。针对水力喷射泵应用于携砂采油存在的技术缺欠,研制了防砂埋套管水力喷射泵。分析了其它水力喷射泵的技术缺欠,提出了从套管注动力液、液力起下泵芯的技术思路,进行了泵研制和室内实验,介绍了套管水力喷射泵的结构、技术原理、技术特点及现场排砂采油应用情况。通过14井次试验表明,防砂埋套管水力喷射泵具有以下技术特点:工作特性符合普通射流泵的特性曲线、液力投捞泵芯,调整泵性能参数、可正洗井,清除油管结蜡、可随时录取油井生产流压、可有效避免地层砂埋封隔器及采油管柱等技术优点,适应含砂小于8%油井,最大排量150m3/d,泵使用寿命大于90d。     

地震场地的综合评定方法

本文给出了一个考虑场地土层的刚度、覆盖土层厚度及软弱夹层、液化土层等因素对场地地震动影响的综合评定方法。该方法根据场地土层的刚度和覆盖土层的厚度，按模糊评判方法确定场地指数μ值，并建立μ值与设计地震反应谱的关系。当场地指数确定时，就可确定用于抗震设计的反应谱。对于场地土层中含有软弱夹层或液化土层的情况，本文还给出了考虑这些影响因素，对场地指数或设计地震动参数进行修正的方法。     

大柳树、小观音坝址区域构造稳定性及岩体质量对比

黑山峡河段开发方式的争论已近半个多世纪，至今仍无结果。就地质方面而言，两坝址区域构造稳定性和岩体质量是核心问题。依据前期大量的勘探、试验资料，并以国家有关规范为标准，对两坝址区域构造稳定性和岩体质量进行了分析对比，认为小观音坝址区域构造稳定性较好，岩体质量优良，为一适宜兴建高混凝土拱坝的优良坝址。大柳树坝址位于中卫～同心断裂带带内，区内曾遭受了Ⅸ～Ⅹ度的历史地震和古地震破坏，坝轴线距全新世活断层仅1．5km，坝址地震基本烈度为Ⅶ度，区域构造稳定性差。坝址区岩体松动破碎，质量差。从施工可能遇到的难题和运行期的稳定考虑，在大柳树建高坝存在重大安全风险。     

DCIM－30集散型控制系统及其在油田中的应用

采用系统集成技术和实用性支持软件相结合的方法，由一个中心操作站和四个现场控制站及ＢＩＴＢＵＳ拓朴网络构成的ＤＣＩＭ－３０集散控制系统，适于在油田多种生产场合推广应用。     

Context Sequence Matching for XML

Context and sequence variables allow matching to explore term-trees both in depth and in breadth. It makes context sequence matching a suitable computational mechanism for a rule-based language to query and transform XML, or to specify and verify web sites. Such a language would have advantages of both path-based and pattern-based languages. We develop a context sequence matching algorithm and its extension for regular expression matching, and prove their soundness, termination and completeness properties.